We love the Born Free bottles and have used them since we started supplementing with formula when our daughter was 3 and a half weeks. However, we have found that the flow rate on the level one Born Free nipple is a little too fast for her. They allow her to gulp down a bottle much to quickly and also make her fussy at the breast. She also started spitting up as soon as we started her on bottles even with the Born Free colic inserts. We started using the Avent level one newborn nipples on the Born Free bottles. The Avent nipples are a little stiffer and have a much slower flow rate. She's doing quite well with this combination and tends to take longer to finish up a bottle and she also spits up less now. We're saving the level one nipples that came with the Born Free bottles until she's a little older and completely weaned from breastfeeding.